Hi! I have a 13" Silver Macbook, and Logitech Z506 surround sound speakers. I want to set it up so that it plays surround sound instead of stereo. Do I need a sound card? What kind is highly recommend? Whats out there for a good price? If i don't get a sound card, what do I do? Thanks

Ok so I found out that my speakers use an analog system where there are two cables, one is just for the stereo, and the other is for the other speakers, because it is like two stereo cables connected together, in this case, i think i do need a sound card. So, what do you guys and girls recommend?